LESSON THIRTEEN. THE AERIAL.The aerial system or antenna might be termed the mouth and ear of the wireless station, for it is this huge network of wires stretching high into the air that emits or intercepts the electromagnetic waves upon which such systems of communication depend.FIG. 28. General Types of AerialsFIG. 28. General Types of AerialsThe value of an aerial is dependent upon its height above the surface of the earth. The greater its height the wider will be the field of force or strain set up in its neighborhood and consequently more powerful electric waves will be developed. Proximity to all large conductors, such as smokestacks, telephone lines, etc., is always avoided because these obstacles would absorb appreciable amounts of the energy sent out from the station and also shield it somewhat from the incoming waves. Aerials are usually constructed of conductors made up of a number of wires stranded together. High frequency currents only travel near the surface of conductors and stranded wires consequently offer less resistance because they possess more surface than a solid conductor of equal cross section.The aerial is always carefully insulated by means of special high tension insulators, made of insulating composition molded into a corrugated bar having iron rings embedded in each end to which the wires may be fastened.Aerials take many different forms, but may be classified into two general groups called the vertical aerials and flat top aerials.Vertical aerials compose thegrid,fan,cageandumbrellaforms.Flat top aerials are known as theT,inverted U,LandVtypes, according to their shape.The Pyramid Aerial is only employed in ultra-powerful stations and is becoming an obsolete form.The Fan Aerial is a good type of especial value in crowded quarters.The Grid Aerial is probably the best form of vertical aerial, but is gradually giving way to those of the flat top class.The Cage Aerial is rarely used nowadays and may be considered obsolete.The Umbrella Aerial is a very good type now being employed in many high power stations. A metallic pole or mast insulated at the base used to support the wires, so that it is part of the aerial itself.The "T" Aerial is the most nearly perfect and gives the best "all around" results.The "L" or Horizontal type of aerial is used wherever it is desirable for any reason to send the most powerful waves in one direction.The "V" type is used where the highest point must be near the station.The wire leading into the station, from the aerial is called the "rat-tail" or "lead-in." It is always very carefully insulated and usually enters the station through a hole in the window or wall by means of a "window pane bushing" or "leading-in insulator."Certain aerials possess a directive action, that is they radiate and receive messages in some directions better than others. Flat top aerials possess this peculiarity more noticeably than the vertical types. Flat top aerials receive and radiate waves coming from and going towards a direction opposite to that in which the free end points.FIG. 29. Spiral Aerial.FIG. 29. Spiral Aerial.The free end is the opposite end to that to which the "rat-tail" is connected.There are two free ends on a "T" aerial and so this form radiates and receives its waves equally well in two directions.The inverted "L" and "V" types possess a very decided directive action.Certain aerial forms may be classed as loop and straightaway accordingly as they are connected and led into the station. In the straightaway form of antenna, the wires are connected together as a whole and one rat-tail led into the station. In the loop form the wires are all connected together and divided into two sections. Two wires are led into the station.The loop form gives slightly better results in a short aerial, but in most cases the straight away is decidedly the most efficient.
LESSON THIRTEEN. THE AERIAL.The aerial system or antenna might be termed the mouth and ear of the wireless station, for it is this huge network of wires stretching high into the air that emits or intercepts the electromagnetic waves upon which such systems of communication depend.FIG. 28. General Types of AerialsFIG. 28. General Types of AerialsThe value of an aerial is dependent upon its height above the surface of the earth. The greater its height the wider will be the field of force or strain set up in its neighborhood and consequently more powerful electric waves will be developed. Proximity to all large conductors, such as smokestacks, telephone lines, etc., is always avoided because these obstacles would absorb appreciable amounts of the energy sent out from the station and also shield it somewhat from the incoming waves. Aerials are usually constructed of conductors made up of a number of wires stranded together. High frequency currents only travel near the surface of conductors and stranded wires consequently offer less resistance because they possess more surface than a solid conductor of equal cross section.The aerial is always carefully insulated by means of special high tension insulators, made of insulating composition molded into a corrugated bar having iron rings embedded in each end to which the wires may be fastened.Aerials take many different forms, but may be classified into two general groups called the vertical aerials and flat top aerials.Vertical aerials compose thegrid,fan,cageandumbrellaforms.Flat top aerials are known as theT,inverted U,LandVtypes, according to their shape.The Pyramid Aerial is only employed in ultra-powerful stations and is becoming an obsolete form.The Fan Aerial is a good type of especial value in crowded quarters.The Grid Aerial is probably the best form of vertical aerial, but is gradually giving way to those of the flat top class.The Cage Aerial is rarely used nowadays and may be considered obsolete.The Umbrella Aerial is a very good type now being employed in many high power stations. A metallic pole or mast insulated at the base used to support the wires, so that it is part of the aerial itself.The "T" Aerial is the most nearly perfect and gives the best "all around" results.The "L" or Horizontal type of aerial is used wherever it is desirable for any reason to send the most powerful waves in one direction.The "V" type is used where the highest point must be near the station.The wire leading into the station, from the aerial is called the "rat-tail" or "lead-in." It is always very carefully insulated and usually enters the station through a hole in the window or wall by means of a "window pane bushing" or "leading-in insulator."Certain aerials possess a directive action, that is they radiate and receive messages in some directions better than others. Flat top aerials possess this peculiarity more noticeably than the vertical types. Flat top aerials receive and radiate waves coming from and going towards a direction opposite to that in which the free end points.FIG. 29. Spiral Aerial.FIG. 29. Spiral Aerial.The free end is the opposite end to that to which the "rat-tail" is connected.There are two free ends on a "T" aerial and so this form radiates and receives its waves equally well in two directions.The inverted "L" and "V" types possess a very decided directive action.Certain aerial forms may be classed as loop and straightaway accordingly as they are connected and led into the station. In the straightaway form of antenna, the wires are connected together as a whole and one rat-tail led into the station. In the loop form the wires are all connected together and divided into two sections. Two wires are led into the station.The loop form gives slightly better results in a short aerial, but in most cases the straight away is decidedly the most efficient.
LESSON THIRTEEN. THE AERIAL.The aerial system or antenna might be termed the mouth and ear of the wireless station, for it is this huge network of wires stretching high into the air that emits or intercepts the electromagnetic waves upon which such systems of communication depend.FIG. 28. General Types of AerialsFIG. 28. General Types of AerialsThe value of an aerial is dependent upon its height above the surface of the earth. The greater its height the wider will be the field of force or strain set up in its neighborhood and consequently more powerful electric waves will be developed. Proximity to all large conductors, such as smokestacks, telephone lines, etc., is always avoided because these obstacles would absorb appreciable amounts of the energy sent out from the station and also shield it somewhat from the incoming waves. Aerials are usually constructed of conductors made up of a number of wires stranded together. High frequency currents only travel near the surface of conductors and stranded wires consequently offer less resistance because they possess more surface than a solid conductor of equal cross section.The aerial is always carefully insulated by means of special high tension insulators, made of insulating composition molded into a corrugated bar having iron rings embedded in each end to which the wires may be fastened.Aerials take many different forms, but may be classified into two general groups called the vertical aerials and flat top aerials.Vertical aerials compose thegrid,fan,cageandumbrellaforms.Flat top aerials are known as theT,inverted U,LandVtypes, according to their shape.The Pyramid Aerial is only employed in ultra-powerful stations and is becoming an obsolete form.The Fan Aerial is a good type of especial value in crowded quarters.The Grid Aerial is probably the best form of vertical aerial, but is gradually giving way to those of the flat top class.The Cage Aerial is rarely used nowadays and may be considered obsolete.The Umbrella Aerial is a very good type now being employed in many high power stations. A metallic pole or mast insulated at the base used to support the wires, so that it is part of the aerial itself.The "T" Aerial is the most nearly perfect and gives the best "all around" results.The "L" or Horizontal type of aerial is used wherever it is desirable for any reason to send the most powerful waves in one direction.The "V" type is used where the highest point must be near the station.The wire leading into the station, from the aerial is called the "rat-tail" or "lead-in." It is always very carefully insulated and usually enters the station through a hole in the window or wall by means of a "window pane bushing" or "leading-in insulator."Certain aerials possess a directive action, that is they radiate and receive messages in some directions better than others. Flat top aerials possess this peculiarity more noticeably than the vertical types. Flat top aerials receive and radiate waves coming from and going towards a direction opposite to that in which the free end points.FIG. 29. Spiral Aerial.FIG. 29. Spiral Aerial.The free end is the opposite end to that to which the "rat-tail" is connected.There are two free ends on a "T" aerial and so this form radiates and receives its waves equally well in two directions.The inverted "L" and "V" types possess a very decided directive action.Certain aerial forms may be classed as loop and straightaway accordingly as they are connected and led into the station. In the straightaway form of antenna, the wires are connected together as a whole and one rat-tail led into the station. In the loop form the wires are all connected together and divided into two sections. Two wires are led into the station.The loop form gives slightly better results in a short aerial, but in most cases the straight away is decidedly the most efficient.
The aerial system or antenna might be termed the mouth and ear of the wireless station, for it is this huge network of wires stretching high into the air that emits or intercepts the electromagnetic waves upon which such systems of communication depend.
FIG. 28. General Types of AerialsFIG. 28. General Types of Aerials
FIG. 28. General Types of Aerials
The value of an aerial is dependent upon its height above the surface of the earth. The greater its height the wider will be the field of force or strain set up in its neighborhood and consequently more powerful electric waves will be developed. Proximity to all large conductors, such as smokestacks, telephone lines, etc., is always avoided because these obstacles would absorb appreciable amounts of the energy sent out from the station and also shield it somewhat from the incoming waves. Aerials are usually constructed of conductors made up of a number of wires stranded together. High frequency currents only travel near the surface of conductors and stranded wires consequently offer less resistance because they possess more surface than a solid conductor of equal cross section.
The aerial is always carefully insulated by means of special high tension insulators, made of insulating composition molded into a corrugated bar having iron rings embedded in each end to which the wires may be fastened.
Aerials take many different forms, but may be classified into two general groups called the vertical aerials and flat top aerials.
Vertical aerials compose thegrid,fan,cageandumbrellaforms.
Flat top aerials are known as theT,inverted U,LandVtypes, according to their shape.
The Pyramid Aerial is only employed in ultra-powerful stations and is becoming an obsolete form.
The Fan Aerial is a good type of especial value in crowded quarters.
The Grid Aerial is probably the best form of vertical aerial, but is gradually giving way to those of the flat top class.
The Cage Aerial is rarely used nowadays and may be considered obsolete.
The Umbrella Aerial is a very good type now being employed in many high power stations. A metallic pole or mast insulated at the base used to support the wires, so that it is part of the aerial itself.
The "T" Aerial is the most nearly perfect and gives the best "all around" results.
The "L" or Horizontal type of aerial is used wherever it is desirable for any reason to send the most powerful waves in one direction.
The "V" type is used where the highest point must be near the station.
The wire leading into the station, from the aerial is called the "rat-tail" or "lead-in." It is always very carefully insulated and usually enters the station through a hole in the window or wall by means of a "window pane bushing" or "leading-in insulator."
Certain aerials possess a directive action, that is they radiate and receive messages in some directions better than others. Flat top aerials possess this peculiarity more noticeably than the vertical types. Flat top aerials receive and radiate waves coming from and going towards a direction opposite to that in which the free end points.
FIG. 29. Spiral Aerial.FIG. 29. Spiral Aerial.
FIG. 29. Spiral Aerial.
The free end is the opposite end to that to which the "rat-tail" is connected.
There are two free ends on a "T" aerial and so this form radiates and receives its waves equally well in two directions.
The inverted "L" and "V" types possess a very decided directive action.
Certain aerial forms may be classed as loop and straightaway accordingly as they are connected and led into the station. In the straightaway form of antenna, the wires are connected together as a whole and one rat-tail led into the station. In the loop form the wires are all connected together and divided into two sections. Two wires are led into the station.
The loop form gives slightly better results in a short aerial, but in most cases the straight away is decidedly the most efficient.